Lomonosov is a medium crater on Mars, with a diameter close to 150 km. It is located in the Martian northern plains north of the planet's equator. Since it is large and found close to the boundary. The topography is smooth and young in this area, hence Lomonosov is easy to spot on large maps of Mars. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mars large craters are named after deceased scientists, writers and others who have contributed to the lore of Mars. Small creaters (less than 60km) are named after small towns and villages.